A surgical microscope of the kind described above is known from U.S. Pat. No. 5,795,295. Here, a surgical microscope is described having a microscope main objective through which a stereoscopic viewing beam path passes. A zoom system for variable magnification is assigned to the microscope main objective. The surgical microscope contains an OCT-system. This OCT-system includes a component assembly for generating an OCT-scanning beam of short coherent laser radiation and further includes an analyzer unit for evaluating interference signals. A unit for scanning the OCT-scanning beam is assigned to this component assembly. The unit for scanning contains two scan mirrors, which can be displaced about two movement axes, in order to scan a surgical region with the OCT-scanning beam. In the surgical microscope in U.S. Pat. No. 5,795,295, the OCT-scanning beam is coupled into the illuminating beam path of the surgical microscope via a divider mirror and, with this illuminating beam path, the OCT-scanning beam is directed through the microscope main objective.
A non-invasive examination and measurement of the structures within a biological tissue are made possible by the method of the optical coherence tomography (OCT). As an image providing process, the optical coherence tomography permits especially section images or volume images of biological tissue to be generated with micrometer resolution. A corresponding OCT-system includes a source for time-dependent incoherent and spatially coherent light having a specific coherence length which is guided to a specimen beam path and a reference beam path. The specimen beam path is directed onto the tissue to be examined. Laser radiation, which is radiated back into the specimen beam path because of scatter centers in the tissue, superposes the OCT-system with laser radiation from the reference beam path. An interference signal develops because of the superposition. The position of the scatter centers for the laser radiation in the examined tissue can be determined from this interference signal.
For OCT-systems, the building principles of the “time-domain OCT” and of the “Fourier-domain OCT” are known.
The configuration of a “time-domain OCT” is described, for example, in U.S. Pat. No. 5,321,501 with reference to FIG. 1a at column 5, line 40, to column 11, line 10. In a system of this kind, the optical path length of the reference beam path is continuously varied via a rapidly moving reference mirror. The light from specimen beam path and reference beam path is superposed on a photo detector. When the optical path lengths of the specimen and reference beam paths are coincident, then an interference signal is provided on the photo detector.
A “Fourier-domain OCT” is, for example, described in international patent publication WO 2006/100544 A1. To measure the optical path length of a specimen beam path, light from the specimen beam path is superposed onto light from a reference beam path. In contrast to the time-domain OCT, the light from the specimen beam path and reference beam path is not supplied directly to a detector for a measurement of the optical path length of the specimen beam path but is first spectrally dispersed by means of a spectrometer. The spectral intensity of the superposed signal generated in this manner from specimen beam path and reference beam path is then detected by a detector. By evaluating the detector signal, the optical path length of the specimen beam path can be determined.
U.S. patent publication US 2002/118449 A1 discloses a surgical microscope which permits a viewing person to examine a surgical region with a stereoscopic viewing beam path by looking into an ocular. The surgical microscope contains a unit for reflecting in data with a display and a beam splitter configured as a divider cube. This beam splitter is mounted in the base body of the surgical microscope in the parallel viewing beam path between the microscope main objective and the ocular. The beam splitter superposes a display image onto the parallel viewing beam in the surgical microscope. The display image is imaged at infinity with a display optic.